Can anyone explain me why the last query returns always 1 row. it should return more than 1 because there're a lot of records in the database!
Sorry for my bad english
$query=mysql_query("SELECT book_id FROM ".DB_PREF."books_cats_list WHERE cat_id='".$cat."'");
if($row=mysql_num_rows($query))
{
//fetching all books from $cat category
for($i=0; $fetch=mysql_fetch_assoc($query); $i++)
{
$records[$i]=$fetch['book_id'];
}
//Joining all records in a string for next query
$records=implode(",",$records);
//returning num rows if there're book_id records in $records array
$query=mysql_query("SELECT * FROM ".DB_PREF."books WHERE book_id IN ('".$records."')");
$rows=mysql_num_rows($query);
echo $rows;
Your query is going to look like this:
SELECT * FROM books WHERE book_id IN ('2,3,4,5')
Note how inside the IN, it's all one string. This one string will be converted to an int. This happens by stopping at the 1st non-number character. So, the query becomes:
SELECT * FROM books WHERE book_id IN (2)
Try to remove the single quotes inside the IN.
NOTE: If your values aren't ints, try changing the the implode to: implode("','",$records), and keep the quotes inside the IN.
At a quick glance I suggest the for loop:
for($i=0; $fetch=mysql_fetch_assoc($query); $i++)
Should be a while loop:
while($fetch=mysql_fetch_assoc($query))
I expect it is only doing one record with that for loop code.
I suggest however you do a left join select
SELECT * FROM books_cats_list as cat
left join books as book on cat.book_id = book.book_id
WHERE cat.cat_id='$cat'
This will be far more optimal in terms of database performance I expect.
Related
I have this query:
$butacas= $this->pdo->prepare('SELECT COUNT( * ) FROM `usuarios` WHERE `sala` LIKE :nombreSala');
$butacas->bindValue(':nombreSala', $nombreSala);
$butacas->execute();
echo $butacas->rowCount();
This query results in an integer: 1
if I replace :nombreSala with the value that actually exists in the database, like:
SELECT COUNT( * ) FROM usuarios WHERE sala LIKE 'salaChica'
It still results in 1.
Now, when checking the database with phpMyadmin I realise that with that value (salaChica) there are 2 items instead of one! (and consulting from phpMyadmin does result in 2).
Why it is not accurate? I've read this post about that function not being always accurate with SELECT, but is there a simple alternative?
You're confusing the number of rows returned (1) with the value returned (2).
Your query "SELECT count(*) WHERE whatever" will always return 1 row (unless you do a group by). that row contains a single column - the value of that column will be the count - 2 in your case.
Try
echo $butacas->fetchColumn();
instead of
echo $butacas->rowCount();
I am learning how to work with MySQL, and at the moment I succeed to show data from my table, using:
while($objResult2 = mysqli_fetch_assoc($objQuery_product)) {
Results are shown by using this variable $objResult2["id_product"]; this way i can take from DB any field I want like: $objResult2["name"]; $objResult2["email"]; etc.
But what i do if i have in the table more rows with the same id_product?
I want to write a if statment, which counts if id_product repeats. How to do that? If it is a lot of work, atleast please give me an idea of the right tutorial that I must read. Because i am trying second day to fix this, and searched google but i didnt find what i need, or maybe i coulndt understand it....
This is my query
$sql_product = "SELECT * FROM ps_product AS prod";
$join_product = " LEFT JOIN ps_product_lang AS lang ON lang.id_product = prod.id_product";
$join2_product = " LEFT JOIN ps_stock_available AS stok ON stok.id_product = prod.id_product";
$where_product =" WHERE prod.id_category_default = $idp AND lang.id_lang = 8";
$sql_product = $sql_product.$join_product.$join2_product.$where_product;
$objQuery_product = mysqli_query($objConnect, $sql_product) or die ("Error Query [".$sql_product."]");
You can simple remove the same id_product using DISTINCT keyword in your query. Such as:
SELECT DISTINCT id_product FROM my_table
This will give you results with different ids only.
The second way of doing it is taking the output values inside an array.
In your while loop:
$my_array[] = $objResult2["id_product"];
Then using array_filter remove all the duplicates inside the array.
YOu can also use array_count_values() if you want to count the duplicate values.
Ok here we go. For example you are fetching data with this query.
select id_product, name from PRODUCTS;
Suppose above query gives you 5 records.
id_product name
1 bat
2 hockey
2 hockey
3 shoes
4 gloves
Now you got 2,2 and hockey, hockey. Instead of thinking this way that you have to introduce an if statement to filter repeating records or same name or id_product records.
Rewrite your sql query like this.
select distinct id_product, name from PRODUCTS;
Or if you need count of each then my friend you will write your query something like this...
Graham Ritchie, if Andrei needs count of each repeating record then we will do something like this in our query.
SELECT PRODUCT_ID,
COUNT(PRODUCT_ID) AS Num_Of_Occurrences
FROM PRODUCTS
GROUP BY PRODUCT_ID
HAVING ( COUNT(PRODUCT_ID) > 1 );
SELECT id_product,COUNT(*) AS count
FROM tablename
GROUP BY id_product;
This query will then return you two items in your query
$objResult2["id_product"] //and
$objResult2["count"]
The if statement is then just
if($objResult2["count"] > 1){
//Do whatever you want to do with items with more than 1 occurence.
//for this example we will echo out all of the `product_id` that occur more than once.
echo $objResult2["id_product"] . " occurs more than once in the database<br/>";
}
I'm trying to add a single column in a db query result. I've read about the SUM(col_name) as TOTAL, GROUP BY (col_name2).
But is there a way i can only SUM the column without any GROUPing? I a case whereby all col_name2 are all unique.
For example... I have a result with the following col headers:
course_code
course_title
course_unit
score
grade
Assuming this have 12 rows returned into an HTML table. Now i want to perform SUM() on all the values (12 rows) for the column course_unit, in other to implement a GPA school grading system.
How can i achieve this.
Thanks.
SELECT SUM(col_name) as 'total' FROM <table>
GROUP BY is required only if you want to sum subsets of the rows in the table.
You can find sum or any aggregate db functions (such as count, avg, etc) for most cases without using group clause. Your sql query may look something like this:
SELECT SUM(course_unit) as "Total" FROM <table_name>;
As comments below have already pointed out: SELECT SUM(course_unit) AS total FROM your_table;. Note that this is a separate query to the one with which you retrieve the table data.
This does it in php. I'm not sure how to do it with pure sql
$query = "SELECT * FROM table";
$result = mysql_query($query);
$sum = 0;
while($row = mysql_fetch_assoc($result))
{
$sum+= intval($row['course_unit']);
}
echo $sum;
SELECT
course_code,
course_title,
course_unit,
score, grade,
(select sum(course_unit) from TableA) total
from TableA;
I need to select category ids from my sql database.
I have a variable $product_id and for each product id there are three rows in a table that i need to select using PHP.
If I do "SELECT * FROM table_name WHERE product_id='$prodid'"; I only get the one on the top.
How can I select all three category_ids which contain the same product_id?
I suppose you are using PHP's mysql functions, is this correct? I am figuring that your query is actually returning all three rows but you aren't fetching all of them.
$sql = "SELECT * FROM table_name WHERE product_id='$prodid'";
$r = mysql_query($sql, $conn); //where $conn is your connection
$x = mysql_fetch_SOMETHING($r); //where something is array, assoc, object, etc.
The fetch function gives only one row at a time. You say you need three so it needs to be executed three times.
$x[0] = mysql_fetch_assoc($r);
$x[1] = mysql_fetch_assoc($r);
$x[2] = mysql_fetch_assoc($r);
OR this would be better
while($curRow = mysql_fetch_assoc($r)) //this returns false when its out of rows, returns false
{
$categoryIds[] = $curRow['category_id'];
}
If this doesn't do it then your query is actually returning only one row and we need to see your tables/fields and maybe sample data.
SQL seems to be correct, but Why do you store product_id in categories table? if it's one-to-many relation it would be better to store only category_id in products table.
The SQL query is correct for what you want to do. It will select all the records in table_name with the field product_id = $prodid (not only 1 or 3 but any that matches the variable)
To select a few records you should use the LIMIT keyword
You should look inside your table structure and the variable $prodid to find problems.
If I need to know the total number of rows in a table of database I do something like this:
$query = "SELECT * FROM tablename WHERE link='1';";
$result = mysql_query($query);
$count = mysql_num_rows($result);
Updated: I made a mistake, above is my actual way. I apologize to all
So you see the total number of data is recovered scanning through the entire database.
Is there a better way?
$query = "SELECT COUNT(*) FROM tablename WHERE link = '1'";
$result = mysql_query($query);
$count = mysql_result($result, 0);
This means you aren't transferring all your data between the database and PHP, which is obviously a huge waste of time and resources.
For what it's worth, your code wouldn't actually count the number of rows - it'd give you 2x the number of columns, as you're counting the number of items in an array representing a single row (and mysql_fetch_array gives you two entries in the array per column - one numerical and one for the column name)
SELECT COUNT(*) FROM tablename WHERE link='1';
You could just do :
SELECT count(*) FROM tablename;
for your query. The result will be a single column containing the number of rows.
If I need to know the total number of rows in a table of database
Maybe I'm missing something here but if you just want to get the total number of rows in a table you don't need a WHERE condition. Just do this:
SELECT COUNT(*) FROM tablename
With the WHERE condition you will only be counting the number of rows that meet this condition.
use below code
$qry=SHOW TABLES FROM 'database_name';
$res=mysql_query($qry);
$output=array();
$i=0;
while($row=mysql_fetch_array($res,MYSQL_NUM)){
++$i;
$sql=SELECT COUNT(*) FROM $row[0];
$output[$i]=mysql_query($sql);
}
$totalRows=array_sum($ouptput);
echo $totalRows;
http://php.net/manual/en/function.mysql-num-rows.php You need this i think.
If you are going to use the following SQL statement:
SELECT COUNT(*) FROM tablename WHERE link='1';
Make sure you have an index on the 'link' column